The present invention relates to a tool damage detection device or the like.
An example of a conventional tool damage detection device is disclosed in Japanese Patent Publication No. TOKKAI 2001-38512. As shown in FIG. 6, this detection device is such that an electric motor 50 is used to detect whether or not a contact bar 51 contacts a body part of a tool 52 which lies within an arc of the contact bar 51. When the contact bar 51 passes without contacting the body part of the tool 52, the electric motor 50 senses this as a “damage” situation, and outputs a warning or a stop signal to a machine control section (not shown in the figure).
However, the above-mentioned detector is often used under circumstances wherein a great amount of cutting agents (liquid) come into contact with the detector, or a mist of cutting agent is filled in the air. Since the cutting agents contain considerable amounts of surfactant, they exhibit extremely high permeability and causticity characteristics. As a result, it is necessary to improve the waterproofing of a bearing of the detector. To do this, it is necessary to provide increased amounts of waterproofing which include the use of rubber O-rings, packing, V-seals and so on. However, these measures induce a shortcoming that the resulting friction resists the rotation of the contact bar and the torque output is reduced.
Also, in the case of the above-mentioned detector, since the cutting agents contain surfactants, they exhibit high levels of permeability and causticity. As a result, the durability of the control motor is significantly reduced due to problems such as failure of the motor coil winding insulation or heat generation due to electric overload. Moreover, an expensive electric control section is required. Additionally, detection of any damage (chipping) due to contact with the edge (slope portion) of the tool which lies within the range of the turning of the contact bar, is almost impossible.
The present invention has been proposed in order to solve the above-mentioned problems. The object of the present invention is, therefore, to provide a tool damage detection device which can detect damage of the body part or edge of the tool without problem occurring due to the penetration of the cutting agents or electric overload which result from the provision of waterproofing measures.
Further objects and advantages of the invention will be apparent from the following description of the invention.